Method and apparatus for laser control during recording

ABSTRACT

The invention relates to recording on a medium, and in particular, to laser control during recording data on an optical medium. A laser control method for dynamically adjusting laser power during recording data onto an optical disc comprises: recording normal data onto the optical disc according to an initial laser power; stopping recording when a trigger is generated; reading back the recorded normal data and generating a first recording quality index; recording a test pattern at a test pattern starting point according to a selected laser power; reading back the test pattern and generating a second recording quality index; and determining an adaptive laser power to continually record the normal data according to the first recording quality index and the second recording quality index.

The present application claims the benefit of U.S. provisionalapplication entitled “METHOD AND APPARATUS FOR LASER CONTROL DURINGRECORDING”, Ser. No. 60/713,206, filed Aug. 31, 2005.

BACKGROUND

The invention relates to recording on a medium, and in particular, tolaser control during data recording on an optical medium.

A conventional method for laser control adjusts a laser power or a writestrategy according to previously recorded data on an optical disc. Thismethod, however, is not able to accurately adjust the required laserpower or write strategy, thus recording quality suffers.

SUMMARY

An object of the invention is to provide a laser control method fordynamically adjusting laser power during recording data onto an opticaldisc. The laser control method comprises: recording normal data onto theoptical disc according to an initial laser power; stopping recordingwhen a trigger is generated; reading back the recorded normal data andgenerating a first recording quality index; recording a test pattern ata test pattern starting point according to a selected laser power;reading back the test pattern and generating a second recording qualityindex, and determining an adaptive laser power to continually record thenormal data according to the first recording quality index and thesecond recording quality index.

Another object of the invention is to provide a laser control method fordynamically adjusting write pulse shape during recording data onto anoptical disc. The laser control method comprises: recording normal dataonto a disc according to an initial write pulse shape; stoppingrecording if a trigger is generated; reading back the recorded normaldata and generating a first recording quality index; recording a testpattern at a test pattern starting point according to a selected writepulse shape; reading back the test pattern and generating a secondrecording quality index, and generating an adaptive write pulse shapecontinually recording the normal data according to the first recordingquality index and the second recording quality index.

A further object of the invention is to provide a laser controlapparatus for dynamically adjusting laser output algorithm to recorddata during recording normal data onto the optical disc. The lasercontrol apparatus comprises: a pick-up head, a write laser modulatingcircuit and a detection circuit. The pick-up head generates laser torecording the normal data onto the optical disc according to the laseroutput algorithm. The detection circuit detects at least one recordingquality index from the data recorded onto the optical disc. The writelaser modulating circuit generates an initial laser output algorithm tothe PUH to record a normal data, generates a stopping signal to stoprecording when receiving a trigger from the detection unit, generates aselected laser output algorithm to the PUH to record a test pattern at atest pattern starting point on the optical disc, and generates anadaptive laser output algorithm to continually record the normal dataaccording to a first recording quality index and a second recordingquality index. The first recording quality index is detected by thedetection unit by reading back the recorded normal data. The secondrecording quality index is detected by the detection unit by readingback the test pattern.

DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example and notintended to limit the invention solely to the embodiments describedherein, will best be understood in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a block diagram of an optical system according to theinvention;

FIG. 2 is a schematic diagram of a recording data segment being recordedinto the disc in FIG. 1;

FIG. 3 is a flow chart of the laser control method according to thefirst embodiment of the invention;

FIG. 4 is a flow chart of the laser control method according to thesecond embodiment of the invention;

FIG. 5 shows a waveform diagram of write strategy determined from thewrite laser modulating circuit, a recorder pit recorded into the disc ofFIG. 1, a sliced signal, and a EFM data clock output from the PLLaccording to the data-to-clock edge deviation method;

FIG. 6A and FIG. 6B show waveform diagrams of DVDR multi-pulse andsingle-pulse write strategies respectively according to a pit/landdeviation;

FIG. 7 shows a waveform diagram of DVDRW multi-pulse write strategy.

DESCRIPTION

A detailed description of the present invention is provided in thefollowing.

A detailed description of the invention is provided in the following.Please refer to FIG. 1 and FIG. 2 at the same time. FIG. 1 is a blockdiagram of an optical system 100 according to an embodiment of theinvention. In some embodiments, the disc 102 may be a recordable DVDdisc (e.g. DVDR and DVDRW) or another type of optical medium. FIG. 2 isa schematic diagram of a recording data segment 200 being recorded ontodisc 102 of FIG. 1. The optical system 100 records normal data 210 ontothe disc 102, and roughly detects some writing quality index back fromthe recorded normal data 210 during recording. For example, the writingquality index could be the bit error rate (BER) detected from the BERmeasurer 112, the jitter detected from the jitter measurer 114, thepit/land length deviation detected from the pit/land length deviationcalculator 116, the data-to-clock edge deviation detected from thedata-to-clock edge deviation calculator 118, and the asymmetry detectedfrom the asymmetry detector 122. When the recording quality indexdeteriorates, the optical system 100 generates a trigger to stoprecording of the normal data 210. For example, the stopping point is thepoint P1 in FIG. 2. Then, the optical system 100 reads the recorded data210 to obtain the accurate writing quality index. After that, theoptical system 100 starts recording the test pattern 220 into the disc102 from the stop point P1 to a predetermined end point P2. The testpattern 220 is recorded onto the disc 102 by another laser power or thewrite strategy. After recording the test pattern 220, the optical system100 can generate a new laser power or write strategy to record thenormal data 230 into the disc 102 according to the information from boththe normal data 210 and the test pattern 220 or the information onlyfrom the test pattern 220. Further description of how to determine thenew laser power or write strategy for recording the normal data 230 isprovided in the following.

In a first embodiment, a detailed description of generating a new laserpower is provided in the following. The normal data 210 is recorded tothe disc 102 according to the laser power PwoA, and the test pattern 220is recorded to the disc 102 according to another laser power PwoB. Ifthe asymmetry read from the normal data 210 is BetaA and the asymmetryread from the test pattern 220 is BetaB, then a new laser power PwoC forrecording the normal pattern 230 can be determined as follows:PowC=PwoA+[(BetaTarget−BetaA)/(BetaB−BetaA)]*(PwoB−PwoA)

wherein the value BetaTarget is a predetermined value. Due to the linearrelationship between the laser power and the asymmetry, the new laserpower PwoC can be determined from the above equation. Additionally, ifthe length of the test pattern 220 requires shortening, a specialpattern utilizing a plurality of long marks (larger than 8T) plus aplurality of short marks (smaller than 5T) can be chosen to fill thetest pattern 220. For example, if the length of test pattern 220 isspecified to be two EFM frames (1 EFM frame=1488T in DVDRspecification), a special pattern(11T+11T+11T+11T+4T+4T+4T+4T+4T+4T+4T+4T+4T+4T+4T+4T) is chosen toappear repeatedly in the test pattern 220 until the test pattern 220 isfilled. Otherwise, if the length of the test pattern 220 is unlimited, arandom pattern is acceptable.

Please refer to FIG. 3. FIG. 3 is a flow chart of the laser controlmethod according to the first embodiment of the invention. The lasercontrol method is applied to the optical system 100. A detaileddescription is given in the following.

Step 302: Start.

Step 304: Start optimum power control (OPC) calibration.

Step 306: Set up an initial laser power PwoA based on the calibrationresults.

Step 308: If the recording has not yet started, step 308 is repeated;otherwise, proceed to step 310.

Step 310: Record the normal data 210 onto the disc 102 by utilizing theinitial laser power PwoA.

Step 312: If the recording is not finished, proceed to step 314;otherwise, go to step 324.

Step 314: Determine if the optical system 100 generates a trigger: Ifyes, proceed to step 316; otherwise proceed to step 310.

Step 316: Stop recording the normal data 210, and read the previouslyrecorded normal data 210.

Step 318: Start recording test pattern 220 at test pattern startingpoint by another laser power PwoB.

Step 320: Stop recording test pattern 220 at test pattern stoppingpoint, and read the test pattern 220 previously recorded.

Step 322: Generate the new laser power PwoC based on the normal data 210and the test pattern 220 previously read.

Step 324: End.

A detailed description of the second embodiment of generating a newwrite strategy is provided in the following. There are various kinds ofwrite strategies; here the write pulse shape is given as an example. Thenormal data 210 is recorded onto the disc 102 according to the writepulse shape WpsA, and the test pattern 220 is recorded onto the disc 102according to another write pulse shape WpsB. The optical system 100 thendetermines the write pulse shape WpsC according to the test pattern 220or/and normal data 210 previously read. For example, if the opticalsystem 100 reads the test pattern 220 and finds it is readable (e.g.asymmetry, jitter, bit error rate, Pit/Land length deviation, ordata-to-clock edge deviation is acceptable), the write pulse shape WpsCcan then be equal to the write pulse shape WpsB. A detailed descriptionof write pulse shape method is provided later.

Please refer to FIG. 4. FIG. 4 is a flow chart of the laser controlmethod according to the second embodiment of the invention. The lasercontrol method is applied to the optical system 100. The detaileddescription is shown as follows.

Step 402: Start.

Step 404: Set up an initial write pulse shape WpsA.

Step 406: If the recording has not yet started, step 406 is repeated;otherwise, proceed to step 408.

Step 408: Record the normal data 210 onto the disc 102 by utilizing theinitial write pulse shape WpsA.

Step 410: If the recording is not finished, proceed to step 412;otherwise, go to step 422.

Step 412: Determine if the optical system 100 generates a trigger: Ifyes, proceed to step 414; otherwise go to step 408.

Step 414: Stop recording the normal data 210, and read the previouslyrecorded normal data 210.

Step 416: Record test pattern 220 at test pattern starting point byanother write pulse shape WpsB.

Step 418: Stop recording test pattern 220 at test pattern stoppingpoint, and read the test pattern 220 previously recorded.

Step 420: Generate the new write pulse shape WpsC based on the normaldata 210 and the test pattern 220.

Step 422: End.

Further description of write pulse shape method is provided in thefollowing. Please Refer to FIG. 5, FIG. 6A, FIG. 6B, and FIG. 7. Forexample, a data-to-clock edge deviation method (FIG. 5) and a Pit/Landlength deviation method (FIG. 6A, FIG. 6B, FIG. 7) are described. FIG. 5shows a waveform diagram of write strategy determined from the writelaser modulating circuit 126 of FIG. 1, a recorder pit recorded onto thedisc 102 of FIG. 1, a sliced signal, and a EFM data clock output fromthe PLL 108 of FIG. 1 according to the data-to-clock edge deviationmethod. By detecting the data-to-clock edge deviation (d1 or d2) fromthe data-to-clock edge deviation calculator 118 (FIG. 1), the writepulse shape times T_(topr) and T_(last) can be adjusted. FIG. 6A andFIG. 6B show waveform diagrams of DVDR multi-pulse and single-pulsewrite strategies respectively according to a pit/land deviation from thepit/land length deviation calculator 116 (FIG. 1). Similarly, FIG. 7shows a waveform diagram of DVDRW multi-pulse write strategy.

Additionally, in some embodiments, the next coming normal data willstart to be recorded at a test pattern starting point after generatingthe new laser power or write strategy; in some embodiments, the nextcoming normal data will start to be recorded at a test pattern stoppingpoint after generating the new laser power or write strategy. In otherwords, the test pattern can be overwritten or not.

Compared with the related art, the laser control method adjusts laserpower or write strategy (write pulse shape) to record the normal patternaccording to both the previous recorded normal data and the recordedtest pattern or according to the recorded test pattern.

While the invention has been described by way of example and in terms ofthe preferred embodiment, it is to be understood that the invention isnot limited thereto. To the contrary, it is intended to cover variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art). Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements.

1. A laser control method for dynamically adjusting laser power duringrecording data onto an optical disc, the laser control methodcomprising: recording normal data onto the optical disc according to aninitial laser power; stopping recording when a trigger is generated;reading back the recorded normal data and generating a first recordingquality index; recording a test pattern at a test pattern starting pointaccording to a selected laser power; reading back the test pattern andgenerating a second recording quality index; and determining an adaptivelaser power to continually record the normal data according to the firstrecording quality index and the second recording quality index.
 2. Thelaser control method of claim 1, wherein the step of recording thenormal data onto the disc further comprises: detecting an on-goingquality index during recording and generating the trigger if on-goingquality index becomes worse than a predetermined value.
 3. The lasercontrol method of claim 2, wherein the on-going quality index, the firstrecording quality index, and the second recording quality are selectedat least one from the group comprised: a asymmetry value, a bit errorrate (BER), a jitter, a pit/land length deviation, or a data-to-clockedge deviation.
 4. The laser control method of claim 1, wherein theadaptive laser power is determined according to the following equation:PowC=PwoA+[(indexTarget−IndexA)/(IndexB−IndexA)]*(PwoB−PwoA) whereinPowA is the initial laser power, PowB is the selected laser power, PowCis the adaptive laser power, IndexA is the first recording qualityindex, IndexB is the second recording quality index, and IndexTarget isa target value of the recording quality.
 5. The laser control method ofclaim 1, wherein the test pattern comprises a plurality of marks longerthan 8T and a plurality of marks shorter than 5T.
 6. The laser controlmethod of claim 5, wherein a length of the test pattern is predeterminedand the test pattern comprised a special pattern appeared repeatedly tomeet the predetermined length.
 7. The laser control method of claim 1,wherein the starting point for recording the test pattern is the pausepoint of the normal data.
 8. The laser control method of claim 1,wherein there is a gap between the starting point for recording the testpattern and the pause point of the normal data.
 9. A laser controlmethod for dynamically adjusting write pulse shape during recording dataonto an optical disc, the laser control method comprising: recordingnormal data onto a disc according to an initial write pulse shape;stopping recording if a trigger is generated; reading back the recordednormal data and generating a first recording quality index; recording atest pattern at a test pattern starting point according to a selectedwrite pulse shape; reading back the test pattern and generating a secondrecording quality index; and generating an adaptive write pulse shapecontinually recording the normal data according to the first recordingquality index and the second recording quality index.
 10. The lasercontrol method of claim 9, wherein the step of recording the normal dataonto the disc further comprises: detecting a on-going quality indexduring recording and generating the trigger if on-going writing qualityindex becomes worse than a predetermined value.
 11. The laser controlmethod of claim 10, wherein the on-going quality index, the firstrecording quality index, and the second recording quality index areselected at least one from the group comprised: a asymmetry value, a biterror rate (BER), a jitter, a pit/land length deviation, a data-to-clockedge deviation, or an asymmetry.
 12. The laser control method of claim9, wherein the test pattern comprises a plurality of marks longer than8T and a plurality of marks shorter than 5T.
 13. The laser controlmethod of claim 12, wherein a length of the test pattern ispredetermined and the test pattern comprised a special pattern appearedrepeatedly to meet the predetermined length.
 14. The laser controlmethod of claim 9, wherein the starting point for recording the testpattern is the pause point of the normal data.
 15. The laser controlmethod of claim 9, wherein there is a gap between the starting point forrecording the test pattern and the pause point of the normal data.
 16. Alaser control apparatus for dynamically adjusting laser output algorithmto record data during recording a normal data onto the optical disc, thelaser control apparatus comprising: a pick-up head (PUH) for generatinglaser to record the normal data onto the optical disc according to thelaser output algorithm; a detection circuit for detecting at least onerecording quality index from the data recorded onto the optical disc;and a write laser modulating circuit for generating an initial laseroutput algorithm to the PUH to record a normal data; generating astopping signal to stop recording when receives a trigger from thedetection unit; generating a selected laser output algorithm to the PUHto record a test pattern at a test pattern starting point on the opticaldisc; and generating an adaptive laser output algorithm to continuallyrecord the normal data according to a first recording quality index anda second recording quality index; wherein the first recording qualityindex is detected by the detection unit by reading back the recordednormal data; and the second recording quality index is detected by thedetection unit by reading back the test pattern.
 17. The laser controlapparatus of claim 16, wherein the detection unit detects an on-goingquality index during recording and generating the trigger if on-goingquality index becomes worse than a predetermined value.
 18. The lasercontrol apparatus of claim 17, wherein the on-going quality index, thefirst recording quality index, and the second recording quality areselected at least one from the group comprised: a asymmetry value, a biterror rate (BER), a jitter, a pit/land length deviation, or adata-to-clock edge deviation.
 19. The laser control apparatus of claim16, wherein the laser output algorithm is the laser power.
 20. The lasercontrol apparatus of claim 19, wherein the write laser modulatingcircuit determines the adaptive laser power according to the followingequation:PowC=PwoA+[(indexTarget−IndexA)/(IndexB−IndexA)]*(PwoB−PwoA) whereinPowA is the initial laser power, PowB is the selected laser power, PowCis the adaptive laser power, IndexA is the first recording qualityindex, IndexB is the second recording quality index, and IndexTarget isa target value of the recording quality.
 21. The laser control apparatusof claim 16, wherein the laser output algorithm is the write pulseshape.
 22. The laser control apparatus of claim 16, wherein the testpattern comprises a plurality of marks longer than 8T and a plurality ofmarks shorter than 5T.
 23. The laser control apparatus of claim 22,wherein a length of the test pattern is predetermined and the testpattern comprised a special pattern appeared repeatedly to meet thepredetermined length.
 24. The laser control apparatus of claim 16,wherein the starting point for recording the test pattern is the pausepoint of the normal data.
 25. The laser control apparatus of claim 16,wherein there is a gap between the starting point for recording the testpattern and the pause point of the normal data.